In S1 radiculopathy, which reflex is decreased?

In S1 radiculopathy, which reflex is decreased?

• A. Patellar tendon
• B. Achilles tendon
• C. Biceps reflex
• D. Triceps reflex

Answer: (B)

S1 radiculopathy most often reduces the ankle jerk because the Achilles reflex is mediated mainly by the S1 nerve root. When S1 is irritated or compressed, the monosynaptic reflex to the gastrocnemius-soleus muscles weakens, leading to a decreased or absent Achilles reflex. The patellar reflex involves the L4 level, while the biceps and triceps reflexes involve C5-C6 and C7-C8, so they are not typically affected in S1 radiculopathy. Clinically, you may also see weakness in plantar flexion and sensory changes in the S1 dermatome along the posterior calf and lateral foot.

S1 radiculopathy most often reduces the ankle jerk because the Achilles reflex is mediated mainly by the S1 nerve root. When S1 is irritated or compressed, the monosynaptic reflex to the gastrocnemius-soleus muscles weakens, leading to a decreased or absent Achilles reflex. The patellar reflex involves the L4 level, while the biceps and triceps reflexes involve C5-C6 and C7-C8, so they are not typically affected in S1 radiculopathy. Clinically, you may also see weakness in plantar flexion and sensory changes in the S1 dermatome along the posterior calf and lateral foot.